Exploring the Atmosphere of Exoplanets- Search for Biosignature

The systematic scientific quest for “habitable” planets and hence a possible
answer to the eternal query of mankind - if we are alone or if life is a
common phenomenon in the Universe, rekindled with the discovery of a
Jupiter size planet orbiting a Sun-like star 51 Pegasi in 1995 by Michel
Mayor and Didier Queloz of Geneva Observatory. Soon, astronomers of
various countries started hunting for new planets by using all available
ground-based telescopes as well as dedicated telescopes in space.
Consequently, a large number of Extra-solar planets orbiting stars of
various kinds were discovered and the diversity in the physical properties
of these planets revolutionized our concept on planets, planetary systems
and their formation. In particular rocky planets in the habitable zone of
a star where the ambient temperature can support water to exist in liquid form have
become the main focus. A good number of rocky planets orbiting within the
habitable zones of low-mass stars are discovered and the upcoming next
generation ground and space-bound observing facilities will enable
discovery of rocky planets in the habitable zone of Sun-like stars.
Therefore, the next step is to probe the atmosphere of such “Habitable”
planets and search for bio-signature in their spectra. In this lecture I
shall present the background as well as the current status of research on
the atmosphere of exoplanets with an emphasis on the habitable planets.